JP2010083223A - Vehicular air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air conditioner with a ventilation function capable of being stably operated when a temperature of outside air is changed. <P>SOLUTION: This conditioner comprises an exhaust fan for exhausting air in a compartment to the outside of the compartment, a refrigerating cycle sequentially connecting a compressor, a condenser, a pressure-reduction means and an evaporator with a refrigerant pipe in an annular manner, a ventilating heat exchanger arranged between the condenser and the pressure-reduction means and exchanging the heat between the air exhausted to the outside of the compartment by the exhaust fan and a refrigerant in the refrigerating cycle, and a bypass circuit communicating the refrigerant pipe connecting the condenser and the ventilating heat exchanger with a refrigerant pipe connecting the compressor and the condenser. A control valve for making a communication condition of the bypass circuit variable is provided on the bypass circuit. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle air conditioner.

  A railway vehicle equipped with a vehicle interior ventilation device has a problem that the air conditioning load is large because the outdoor air that is hotter than the interior of the vehicle is taken into the vehicle interior by ventilation and the cold interior air is discharged to the outside air.

  Further, in order to suppress an increase in air conditioning load due to ventilation in a general house, Patent Document 1 discloses a ventilation auxiliary circuit formed by connecting a ventilation air supply heat exchanger, a decompressor, and a ventilation exhaust heat exchanger in series. In addition, a technique is disclosed in which the ventilation intake air heat exchanger is positioned on the indoor heat exchanger side in the direction of the refrigerant flow during cooling and provided on the upstream side of the indoor heat exchanger. According to Patent Document 1, precooling of ventilation supply air and exhaust heat recovery of ventilation exhaust air can be performed via a refrigerant, and energy saving can be improved.

Japanese Patent Laid-Open No. 11-257793

  In the vehicle air conditioner, not only there are many passengers in a narrow passenger compartment, but also the influence of solar radiation load is large, so that a cooling load may be generated even when the outside air temperature is relatively low. FIG. 6 shows a ph diagram when the outside air temperature changes. The solid line indicates a refrigeration cycle at a high outside air temperature, and the broken line indicates a refrigeration cycle at a low outside air temperature. As the outside air temperature decreases, the evaporation enthalpy difference in the evaporator increases from Δh to Δh ′ as can be seen from the figure, and the evaporation temperature also decreases with this change. When this decrease width becomes large, there is a possibility that the evaporating temperature is lowered to the freezing temperature.

  By the way, in Patent Document 1, a ventilation exhaust heat exchanger that performs heat exchange between the high-temperature liquid refrigerant flowing out of the condenser and the relatively low-temperature ventilation exhaust air is provided. By increasing the degree of cooling, the evaporation enthalpy difference, that is, the cooling capacity is increased, and the air conditioning load due to ventilation can be suppressed.

  At this time, the degree of supercooling at the outlet of the heat exchanger for ventilation exhaust changes depending on the air temperature in the passenger compartment. It is necessary to design the capacity and heat exchanger of the machine. For this reason, on the contrary, under the condition that the degree of supercooling is large, such as when the air temperature in the passenger compartment is low, the cooling capacity becomes excessive. Therefore, as described above, the capacity tends to be excessive under the condition where the outside air temperature is low, and the evaporation temperature may be lowered to the freezing temperature. However, this point has not been taken into consideration in Patent Document 1.

  Moreover, in order to operate the compressor stably, it is necessary to secure a predetermined pressure difference at the compressor inlet / outlet. However, since the condensation temperature also decreases when the outside air decreases, the pressure difference at the compressor inlet / outlet becomes small. Tend. In particular, as shown in Patent Document 1, when the degree of supercooling is increased using ventilated exhaust, the necessary amount of refrigerant circulation at the same cooling capacity decreases, so the amount of heat released from the condenser also decreases and is necessary. Therefore, there is a possibility that it becomes impossible to ensure a sufficient compressor inlet / outlet pressure difference.

  Further, when the outside air temperature is further lowered and the passenger compartment air temperature and the outside air temperature are reversed, the refrigerant cooled and condensed by the condenser may be heated reversely by heat exchange with the ventilation exhaust air. In this case, since the inlet refrigerant state of the decompression means is changed from the liquid single phase to the gas-liquid two-phase state, the decompression width is increased, and there is a possibility of causing problems such as a significant decrease in the evaporation temperature.

  An object of the present invention is to solve the above-described problems and provide an air conditioner that can be operated stably using ventilation exhaust air even at a low outside air temperature.

  In order to solve the above-described problems, an air conditioner for a vehicle according to the present invention includes an exhaust fan for exhausting air in a vehicle compartment to the outside of the vehicle compartment, a compressor, a condenser, a decompression means, and an evaporator in an annular manner in order by refrigerant piping. A ventilation heat exchanger that is disposed between a connected refrigeration cycle, the condenser and the decompression means, and performs heat exchange between the air exhausted out of the passenger compartment by the exhaust fan and the refrigerant in the refrigeration cycle. And a refrigerant circuit connecting the condenser and the ventilation heat exchanger, a bypass circuit connecting the compressor and the condenser, and a communication state of the bypass circuit is variable. A control valve is provided on the bypass circuit.

  ADVANTAGE OF THE INVENTION According to this invention, the air conditioning apparatus which can be drive | operated using the ventilation exhaust air stably also at the time of low external air temperature can be provided.

  The air conditioner according to the embodiment of the present invention will be described in detail below with reference to FIGS.

  A first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a system diagram showing a first embodiment of the present invention. During the cooling operation, the refrigerant (not shown) compressed by the compressor 1 passes through the four-way switching valve 2 as indicated by a solid line and enters the outdoor heat exchanger 3, and in the outdoor heat exchanger 3, the outdoor fan 6 After being condensed by dissipating heat to the outdoor air 50 outside the passenger compartment, the air flows into the ventilation heat exchanger 4. Ventilation exhaust air 51 from the vehicle interior 30 is introduced into the ventilation heat exchanger 4 by a ventilation exhaust fan 9, and the refrigerant is further condensed and liquefied by heat exchange with the ventilation exhaust air 51. Thereafter, the low-temperature and low-pressure refrigerant decompressed by the decompression means 10 evaporates in the indoor heat exchanger 5 and returns to the compressor 1 through the four-way switching valve 2 to constitute a refrigeration cycle. At this time, the air flowing into the indoor heat exchanger 5 is a mixture of the ventilation supply air 53 introduced from the outside of the vehicle interior by the ventilation air supply fan 8 and the indoor extraction air 52 extracted from the vehicle interior 30. Yes, after being cooled by the indoor heat exchanger 5, it is cooled by being blown out into the vehicle interior 30.

  For comparison, FIG. 5 shows a conventional system diagram that does not include a ventilation heat exchanger. In this case, during the cooling operation, the outdoor heat exchanger 3 exchanges heat with the outdoor air 50 outside the passenger compartment, so that the condensed and liquefied refrigerant (not shown) is decompressed as it is by the decompression means 10 and is subjected to indoor heat exchange. 1 differs from the embodiment shown in FIG. 1 in that the ventilated exhaust air 51 exhausted from the ventilating exhaust fan 9 to the outside of the passenger compartment is transferred to the outside of the passenger compartment without exchanging heat with the refrigerant. Exhausted.

  As described above, in the conventional system, the low-temperature ventilation exhaust air is directly discharged to the outside of the passenger compartment. However, in the embodiment shown in FIG. 1, the ventilation heat exchanger 4 that performs heat exchange with the ventilation exhaust air is By arrange | positioning in series with the outdoor heat exchanger 3, the performance of a condenser can be improved and the efficiency of a refrigerating cycle can be improved.

  The efficiency improvement effect of this refrigeration cycle is shown by a ph diagram in FIG. As indicated by the solid line, the refrigerant compressed from the point d to the point a by the compressor 1 radiates heat to the point e by the outdoor heat exchanger 3, and then further radiates and liquefies by the ventilation heat exchanger 4, It reaches b point. Thereafter, the pressure is reduced to the point c by the decompression means 10, and the interior heat exchanger 5 evaporates by taking heat from the air in the passenger compartment to reach the point d. In addition, the cycle shown with the broken line in FIG. 2 has shown the conventional cycle without the heat exchanger 4 for ventilation. In this embodiment, the ventilation heat exchanger 4 is a part of the condenser, so that the condensation pressure can be suppressed.

  Therefore, it is possible to suppress the compression power in the compressor 1 while maintaining the cooling capacity with the same evaporation enthalpy difference, and it is possible to improve energy saving.

  Next, an operation mode when the outside air temperature is lowered in FIG. 1 will be described. When the outside air temperature decreases, the control valve 12 is opened to bypass a part of the refrigerant flowing from the compressor 1 to the outdoor heat exchanger 3, and the bypass refrigerant path 11 flowing directly into the ventilation heat exchanger 4 is used. To do. When the control valve 12 is closed, the refrigerant has flowed into the ventilation heat exchanger 4 after exchanging heat with the outdoor heat exchanger 3, but by opening the control valve 12, some refrigerant is Since the outdoor heat exchanger 3 is bypassed, the refrigerant at the inlet of the ventilation heat exchanger 4 is not sufficiently condensed, and a necessary heat radiation amount in the ventilation heat exchanger 4 is increased. Since it is necessary to increase the temperature difference from the air in order to increase the amount of heat release, the condensation temperature becomes high, and it is possible to suppress a decrease in the condensation temperature at a low outside air temperature. Therefore, it is possible to avoid problems such as a decrease in evaporation temperature.

  Next, this effect is shown using the ph diagram of FIG. The solid line indicates the refrigeration cycle during bypass, and the broken line indicates the refrigeration cycle with the bypass valve closed. When the control valve 12 remains closed, as shown by the broken line, the condensation temperature decreases as the outside air temperature decreases, and the enthalpy difference Δh ′ in the indoor heat exchanger 5 increases. There was a possibility of causing problems. On the other hand, when the control valve 12 is opened, the point f at which the refrigerant at the outlet e of the outdoor heat exchanger 3 and the refrigerant discharged from the compressor 1 at the point a merge becomes the inlet condition of the ventilation heat exchanger 4. Therefore, the enthalpy difference up to point b at the outlet of the heat exchanger 4 for ventilation, that is, the necessary heat dissipation amount increases. By this effect, the condensation temperature rises and the specific enthalpy at the point b at the outlet of the ventilation heat exchanger 4 also increases. For this reason, it is possible to avoid problems due to an increase in the evaporation enthalpy difference in the evaporator.

  Further, in this embodiment, since the condensation temperature can be kept high, a necessary pressure difference in the compressor can be secured at the same time, and stable operation is possible.

  In the present embodiment, the control valve 40 controls the opening and closing of the control valve 12 by detecting the outdoor air temperature flowing into the outdoor heat exchanger 3 by using the temperature detecting means 41. This control may be performed using other temperature information. For example, in this embodiment, the temperature detecting means 42 for measuring the temperature of the refrigerant pipe connecting the outdoor heat exchanger 3 and the ventilation heat exchanger 4 is provided. Since the condensation temperature can be detected using the temperature detection means 42, the open / close state of the control valve 12 can be controlled by a command from the control device 40. Therefore, for example, when the condensation temperature detected by the temperature detection means 42 is lower than a predetermined value, a command to open the control valve 12 can be issued. Rather than detecting and controlling the outside air temperature, it is possible to detect the decrease in the condensation temperature more reliably by directly detecting the condensation temperature. As described above, it is possible to increase the condensation temperature and continue the stable cooling operation.

  In this embodiment, the control valve 12 is a valve that can be opened and closed. However, a plurality of valves may be arranged in parallel or the flow rate may be variable. In this case, the temperature detection means 41 or 42 as described above may be used. Based on the information, the flow rate of the refrigerant flowing through the bypass refrigerant path 11 may be adjusted.

  Further, a temperature detecting means 43 for detecting the inflow temperature of the ventilation exhaust air 51 to the ventilation heat exchanger 4 may be provided, and the condensation temperature detected by the temperature detecting means 42 is always the temperature detecting means 43. It may be controlled so as to be higher than the temperature of the ventilated exhaust air 51 detected in step (1). In this case, it is possible to reliably avoid the situation where the refrigerant condensed in the outdoor heat exchanger 3 is heated in the ventilation heat exchanger 4.

  By the way, a method of providing a bypass for the heat exchanger 4 for ventilation can be considered as one of means for suppressing a decrease in the condensation pressure at a low outside air temperature. In this embodiment, a circuit for bypassing the outdoor heat exchanger with a refrigerant is provided. It was decided to provide it. This is for the purpose of avoiding problems due to refrigerant amount fluctuations. Even when a circuit that bypasses the ventilation heat exchanger 4 is provided, the ventilation exhaust fan is operating, so that the refrigerant in the ventilation heat exchanger 4 and the ventilation exhaust air 51 to be ventilated are always present. The heat will be exchanged. For this reason, the amount of refrigerant in the refrigeration cycle varies according to the relationship between the temperature of the ventilation exhaust air 51 to be ventilated and the condensation temperature.

  That is, when the temperature of the ventilation exhaust air 51 is lower than the condensing temperature, the liquid refrigerant stagnates in the ventilation heat exchanger 4, and the refrigerant amount in the refrigeration cycle may be insufficient. On the other hand, when the temperature of the ventilation exhaust air 51 is higher than the condensation temperature, conversely, the ventilation heat exchanger 4 becomes a gas refrigerant, and the amount of refrigerant in the refrigeration cycle may be excessive. In the present embodiment, in order to avoid such a situation, the outdoor heat exchanger 3 arranged on the upstream side of the outdoor heat exchanger 3 and the ventilation heat exchanger 4 connected in series is partially bypassed. The configuration is such that problems due to the stagnation of refrigerant in the ventilation heat exchanger 4 can be avoided.

  In this embodiment, the ventilation exhaust fan 9 is arranged in the downstream air passage of the ventilation heat exchanger 4. In the ventilation exhaust fan 9, the air temperature rises not only due to the heat generated by the fan motor but also due to adiabatic compression. Therefore, if the ventilation exhaust fan 9 is arranged upstream of the ventilation heat exchanger 4, the temperature difference from the refrigerant is reduced and heat is effectively generated. There is a problem that it cannot be exchanged.

  Therefore, in this embodiment, the ventilation exhaust fan 9 is arranged downstream of the ventilation heat exchanger 4 and the ventilation exhaust air 51 is allowed to flow into the ventilation heat exchanger 4 without increasing the temperature. The heat exchange performance is improved by maintaining a large temperature difference from the refrigerant.

  Further, in the present embodiment, the outdoor heat exchanger 3 and the ventilation heat exchanger 4 are connected by the two refrigerant connection pipes 13 having the same number of paths as the ventilation heat exchanger 4. When both are connected by one pipe, a distributor is required in the ventilation heat exchanger 4, and the refrigerant condensing temperature in the ventilation heat exchanger 4 decreases due to a pressure loss in the distributor, thereby ventilating exhaust. Since a temperature difference with the air 51 becomes small, heat exchange performance will fall. Therefore, in this embodiment, the distributor from the outdoor heat exchanger 3 to the ventilation heat exchanger 4 is connected to the ventilation heat exchanger 4 by connecting the same number of pipes as the number of paths of the ventilation heat exchanger 4. Installation is unnecessary. For this reason, since it can prevent that the condensation temperature of the heat exchanger 4 for ventilation falls by pressure loss, the heat exchange performance with exhaust air can be kept high.

  In the present embodiment, the four-way switching valve 2 is provided to enable switching between the cooling operation and the heating operation. An operation mode when the four-way switching valve 2 is switched will be described. The high-temperature gas refrigerant compressed by the compressor 1 passes through the four-way switching valve 2 as indicated by a broken line, and becomes a mixture of the indoor extracted air 52 and the ventilation supply air 53 extracted from the room by the indoor heat exchanger 5. It is condensed and liquefied by dissipating heat. At this time, the heated air returns to the vehicle interior 30 to perform heating. Thereafter, the refrigerant having a low temperature reduced by the decompression means 10 partially evaporates in the ventilation heat exchanger 4 and then completely evaporates in the outdoor heat exchanger 3 to become a gas refrigerant. Thus, a refrigeration cycle returning to the compressor 1 is configured. At this time, since both the heat exchanger 4 for ventilation and the outdoor heat exchanger 3 function as an evaporator, the evaporation temperature can be increased and the efficiency of the refrigeration cycle can be improved. Furthermore, since the ventilation exhaust air flowing into the ventilation heat exchanger 4 is normally higher than the outside air temperature, the evaporation performance can be improved by using the ventilation heat exchanger 4.

  Therefore, in the present embodiment, it is possible to increase the efficiency of the refrigeration cycle even when the heating operation is performed.

  FIG. 4 shows a ph diagram during heating operation. The refrigerant compressed from the point d to the point a by the compressor 1 radiates heat in the indoor heat exchanger and reaches the point b. Thereafter, the refrigerant depressurized to the point c by the decompression means 10 evaporates to the point e in the ventilation heat exchanger 4, and further evaporates in the outdoor heat exchanger 3, and reaches the point d. In the figure, a refrigeration cycle diagram in a conventional system without the heat exchanger 4 for ventilation is shown by a broken line. Compared to the conventional system, in the cycle of the present embodiment, the evaporator performance can be improved, so the evaporation temperature is high, the compression power in the compressor 1 can be suppressed, and a system with high energy saving can be achieved. Yes.

The block diagram which shows the operation | movement aspect at the time of the air_conditionaing | cooling operation in 1st embodiment of this invention. The ph diagram which shows the operation | movement aspect at the time of the cooling operation in 1st embodiment of this invention. The ph diagram which shows the condensation temperature fall suppression effect at the time of low external temperature. The ph diagram which shows the operation | movement aspect at the time of the heating operation in 1st embodiment of this invention. The block diagram which shows the operation | movement aspect at the time of air_conditionaing | cooling operation in a prior art. The ph diagram which shows the change at the time of the low external temperature in a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Compressor 2 Four-way selector valve 3 Outdoor heat exchanger 4 Ventilation heat exchanger 5 Indoor heat exchanger 6 Outdoor fan 7 Indoor fan 8 Ventilation supply fan 9 Ventilation exhaust fan 10 Decompression means 11 Bypass refrigerant path 12 Control valve 13 Connection piping 30 Car interior 40 Control devices 41, 42, 43 Temperature detection means 50 Outdoor air 51 Ventilation exhaust air 52 Indoor extraction air 53 Ventilation supply air

Claims (5)

  An exhaust fan that exhausts the air in the passenger compartment to the outside of the passenger compartment, a refrigeration cycle in which a compressor, a condenser, a decompression unit, and an evaporator are sequentially connected in an annular manner through a refrigerant pipe, and the condenser and the decompression unit A ventilation heat exchanger arranged to exchange heat between the air exhausted out of the passenger compartment by the exhaust fan and the refrigerant in the refrigeration cycle, and a refrigerant pipe connecting the condenser and the ventilation heat exchanger And a bypass circuit for connecting the compressor and the refrigerant pipe connecting the condenser, and a control valve for changing the communication state of the bypass circuit is provided on the bypass circuit. Air conditioner for vehicles.   2. The vehicle air conditioner according to claim 1, wherein at least one of a temperature of air flowing into the outdoor heat exchanger, a temperature of air flowing into the ventilation heat exchanger, and a condensing temperature during cooling operation. A vehicle comprising: temperature detection means for detecting temperature; and a control unit that performs control to change the opening of the control valve based on temperature information detected by the temperature detection means. Air conditioner for use.   3. The vehicle air conditioner according to claim 2, wherein the temperature detection means for detecting the condensation temperature during cooling operation is disposed in a refrigerant pipe connecting the outdoor heat exchanger and the ventilation heat exchanger. A vehicle air conditioner.   2. The vehicle air conditioner according to claim 1, wherein the exhaust fan is disposed downstream of the ventilation heat exchanger.   2. The vehicle air conditioner according to claim 1, wherein the number of passes at the outlet of the outdoor heat exchanger is equal to the number of passes at the inlet of the heat exchanger for ventilation, and the paths of both heat exchangers are one-to-one. A vehicle air conditioner characterized by being connected to each other by a refrigerant pipe so as to correspond.

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